This invention relates to optical fiber connectors and, more particularly, to an alignment assembly for precision connection of connector ferrules.
Communication by means of optical signals transmitted over optical fibers has become extremely popular and has given rise to a unique and rapidly growing technology. In particular, optical technology is being used more and more in broadband systems where communication is by means of high speed optical channels. The need for efficient utilization of available real estate on circuit boards, racks and shelves, back planes, and distribution channels, etc. is becoming increasingly important as miniaturization proceeds apace, wherein generating, transporting, managing, and delivering broadband service is performed in or by smaller and smaller components. As a consequence, the industry has placed an emphasis on small form factor optical connectors, such as the LC connector from Lucent Technologies Inc. However, miniaturization is tempered by the requirements of transmission efficiency. For instance, with the advent of new standards such as Gigabit Ethernet, wherein the transmission efficiency is becoming more and more critical, the performance of optical connectors is becoming correspondingly important for healthy operation of networks and systems. Thus, it is desirable to obtain component miniaturization without sacrificing transmission efficiency, and preferably while improving transmission efficiency.
With the miniaturization of optical modules and optical fiber devices, the management of optical fiber congestion has become an issue at optical interfaces and connection distribution points. One solution is the use of multi-fiber ribbon in which a plurality of optical fibers are organized and molded side by side in a plastic ribbon. It is known to interconnect these ribbon cables by supporting the fibers between two support members preferably but not necessarily made of a monocrystalline material, such as silicon. In the support members are V-grooves formed utilizing photolithographic masking and etching techniques. The fibers are placed side by side in individual V-grooves of one support member and the other mating support member having corresponding V-grooves is placed over the fibers so as to bind or hold the fibers in a high precision, spatial relationship between the mating V-grooves. The top and bottom support members sandwiching the multi-fiber ribbon are typically bonded together with a clamp or adhesive, forming a ferrule of a multi-fiber connector. Two mating ferrules with the same fiber spacing may then be placed in an abutting relationship so that the ends of the fibers of the respective ferrules are substantially co-axially aligned with one another, thereby forming a multi-fiber connection. If desired, such ferrules can be stacked in order to increase the interconnection density.
Multi-fiber ribbons and connectors have numerous applications in optic communication systems. For instance, some opto-electronic and optical application specific integrated circuits (OASIC) devices, e.g., optical switches, optical power splitters/combiners, routers, etc. have several input and/or output ports arranged as linear arrays to which a plurality of fibers are to be coupled. Further, since optical fibers are attached to launch optical signals into these devices and extract optical signals out of these devices, splicing of arrays of fibers (i.e., a multi-fiber ribbon) to such devices can be achieved using multifiber connectors. Yet another possible application relates to an optical fan-out fabric where an array of fibers in a multi-fiber ribbon may be broken into simplex or duplex channels for distribution purposes, as is often desired.
A critical factor to the optical efficiency of a multi-fiber connector, whether or not stacked, is the precise alignment of the mating ferrules with regard to one another. As the ferrule structures utilized to achieve the precise axial alignment of corresponding optical fibers of a multi-fiber connection become smaller, there exists a need for connectors that are likewise space efficient so that full advantage of the miniaturized ferrule can be realized with higher interconnection density. Further, there also exists the need for multi-fiber connectors to be user friendly so that the operation and utility of the multi-fiber connector is intuitive to the workers that will be installing systems utilizing optical components. For example, it is desirable for multi-fiber connectors to have plug-and-play capability, in that they can be quickly and easily coupled to a piece of equipment, device, or one another. It is common practice in the art today to provide first and second large V-grooves on either side of the array of V-grooves in which the fibers are contained, and parallel thereto. The enlarged V-grooves have mounted and affixed therein, as by cementing, alignment pins which project out of the front face of the ferrule. When a connection is to be made with another ferrule, this other ferrule has the enlarged V-grooves but no alignment pins, so that the alignment pins can fit therein in a male-female connection, to align the two ferrules precisely and, hence, the fibers contained therein. Such a connection is quickly and easily accomplished, thereby fulfilling the user friendly desideratum.
Because of the high frequencies involved as well as the large bandwidths of the signals being transmitted at high speed through the connection, it is essential for optimum alignment of the fibers that the faces of the ferrules be highly polished to a high degree of flatness, and that they be clean or free of even minute accumulations of dirt or dust. To this end, it is desirable that cleaning the ferrules and, more particularly, their front or butting faces, be done from time to time to insure optimum cleanliness. However, because of the alignment pins projecting from the front face, the cleaning and polishing of the ferrule faces is extremely difficult to accomplish both from the standpoint of a complete cleaning and polishing and from the necessity of protecting the alignment pins from damage.
The present invention is directed to making the cleaning, polishing, or re-finishing of a ferrule face from which the alignment pin or pins project an easily performed operation.
In accordance with the principles of the invention, each of the enlarged V-grooves in the support member for containing a locating pin extends from the front face of the ferrule support member toward the rear, parallel to the V-grooves for containing the fibers. A rear portion of the enlarged groove has first and second stop member projecting from opposite walls of the groove forming a restricted space therein forming a chamber which extends to the rear. Each chamber has a bore connecting it to the exterior which is designated as an exhaust port. Thus when, for example, it is desired, after the support members are assembled into a sandwich, as discussed hereinbefore, to clean the enlarged V-grooves, compressed air, for example, may be blown into the passage formed by the enlarged V-grooves, and any dirt or debris is exhausted out of the exhaust ports.
Alignment or guide pins for mounting in the enlarged V-grooves are made of suitable hard, durable material, preferably, but not limited to, necessarily, stainless steel, and each comprises an elongated cylindrical member or rod having a chamfered front end for ease of insertion into the enlarged V-groove of the mating ferrule. The alignment pins may also be made of ceramic material. The rear portion of the rod has a reduced diameter groove wherein the diameter is only slightly less than the lateral spacing of the stop members. Between the chamfered rear end of the rod and the reduced diameter groove is a pair of diametrically opposed flats, the distance between which is slightly less than the lateral spacing of the stop members, being substantially equal to the diameter of the groove. As will be seen hereinafter, the groove has front and rear shoulders spaced apart a distance slightly greater than the length of the stop members. These shoulders prevent the alignment pin from moving axially, thereby functioning to hold the pin in place within its groove. However, the flats eliminate the rear shoulder so that if the pin is rotated to a position where the flats are vertically oriented, the stop members no longer function to prevent axial movement of the pin, and it may be introduced into or withdrawn from the ferrule. With the pin withdrawn and separated from the ferrule, the front face may easily be cleaned and polished, after which the pin (or pins) is reinserted into its V-groove opening in the ferrule, rotated so that the flats are vertical so that the rear portion may be moved into the chamber, and then rotated ninety degrees, for example, so that the front and rear shoulders of the groove embrace the stop members to prevent axial movement of the pin. The process is simply reversed to remove the pin. Thus, the alignment pin need not be cemented in place and can be removed and replaced as needed.
Various principles and features of the present invention will be more readily apparent from the following detailed description, read in conjunction with the accompanying drawings.